Starts off at 7 ends at114688, subtract them, 114681. Now there are 8 terms so subtract 1 because you're starting from the beginning, that leaves 7. Now divide 114681/7=16,383 difference per point, Now 1st pt is 7 2nd is 16390 3rd is 32773 4th is 49156 5th is 65539 6th is 81922 7th is 98305 8th is 114688 Now add these= 458780